Hatch Wing on 2009 Toyota Matrix

[thirdman]

according to my ever-so-questionable research, it will hurt:

[Xringer]

That third image seems to show a better cd with a little flat wing sitting out
about 5 or 6 inches behind the top.. What's up with that?

[Raysp30]

Project for somebody with a little more time and know how than me....

Using the aerodynamic program recently discovered, can somebody sketch a typical sedan and then put a short wing angled down at a nice tear-drop shape.

I'm wondering if I can have a portion of the results that a boat-tail would give while only having a very small wing where the roof line ends.

Taking a guess, I would think it would only help some, but it may be enough to make it worthwhile.

[donee]

Hi All,

Look over the driver on the new Matrix. The roof peaks, and then is downhill towards the aft. So, the thirdman model is incorrect, and not predictive.

The downhill section is going to impart downward movement to the air. If they did not have that extension, flow would seperate in front of the rear of the car a little bit. That the extension is for, to keep the flow from sepearting.

The tip of the spoiler is higher than the lowest portion of the roof. But well below the height of the roof over the driver.

[thirdman]

My model is for a Ford Festiva, and I just posted it as an example.

[gascort]

Originally Posted by Raysp30

Project for somebody with a little more time and know how than me....

Using the aerodynamic program recently discovered, can somebody sketch a typical sedan and then put a short wing angled down at a nice tear-drop shape.

I'm wondering if I can have a portion of the results that a boat-tail would give while only having a very small wing where the roof line ends.

Taking a guess, I would think it would only help some, but it may be enough to make it worthwhile.

You're talking about a Kammback. If you already don't know what they are, do a search about them on here, and look at MetroMPG's current project: making a permanent Kammback extension...

[Raysp30]

Originally Posted by gascort

You're talking about a Kammback. If you already don't know what they are, do a search about them on here, and look at MetroMPG's current project: making a permanent Kammback extension...

Not quite. I'm talking about a Kammback that is only 2-3 inches long.

[Concrete]

I think thirdman is onto something

in the first half this infomercial they show a back view of this concept SAAB
looks like it has active spoilers that extend behind the hatch and under the bumper - but they seem to indicate they are for low drag - "10% reduction"

not unlike what thirdman has shown

YouTube - Efficiency at Work

and I am very interested in the thirdman concept for my truck cab
but expect it may be a very tricky to get it just right
and if it is not right I'm sure it would increase drag
a Kamm back may just be more practical for those of us that don't have wind tunnels

BTW
justpassntime is building a short Kamm back - similar to matrix wing
he says it will be somewhat adjustable during development
could shed some light on this topic to have some real world data
http://ecomodder.com/forum/showthrea...bers-3945.html

[aerohead]

Originally Posted by SuperTrooper

How do you know for sure it doesn't generate any lift? The profile resembles a wing shape to me. Anyway, the problem here is the perspective of the photo. It's shot from ground level giving the appearance that the spoiler tilts up. The rear edge actually winds up horizontal, or parallel to the road surface; which is what you want when breaking airflow away from the body to reduce drag.

I'm given to understand that van and wagon style bodies do not generate the kind of lift that would be found in a fastback or notchback body style.The explanation given, is that the way the air mass is distributed for vans and wagons,yields essentially the same air velocity above the body,as it is alongside.Without the velocity differential,there cannot exist a pressure differential which would induce the lift.Sure,the matrix does have some roof camber,and it occurs directly over the driver's head,and there is some lift associated with deformation of the streamlines,but at normal highway speeds,this would present no challenge to stability,especially something which could be cured by something at the far end of the roof.And actually,if the air could continue rearward,at its defined slope,it would achieve atmospheric pressure at a distance,1.78 times the body height,behind the point of maximum camber.If the hatch wing tilts up,it blasts the airstream into turbulence which cannot recover it's kinetic energy into static pressure,and you're left with higher drag.Air needs about 3.5 more time to decelelerate without separation,than the time it can withstand during acceleration from rest.The long progressively increasing curvature roofline,with no interruptions,provides that gentle deceleration ramp the air needs to reach equilibrium pressure.